This invention relates to an ignition control apparatus for a spark-ignited internal combustion engine. More particularly, it relates to an ignition control apparatus which can prevent improper ignition such as misfiring when an engine is starting.
In order to carry out proper ignition in an internal combustion engine, it is necessary for the current flowing through the primary winding of the ignition coil for the engine to reach a prescribed level. On the other hand, if the primary winding current exceeds this prescribed level, electric power from the storage battery for the engine, which is used to energize the ignition coil, will be needlessly consumed.
Therefore, many engines are equipped with ignition controllers which prevent the primary winding current from exceeding a prescribed current limit. However, conventional ignition controllers of this type have a number of drawbacks. For example, they generally employ elements having characteristics which vary significantly with operating temperature, and as a result a stable primary winding current can not be obtained. Furthermore, at very low engine speeds such as when an engine is cranking, it may be impossible with such ignition controllers to obtain an adequate current in the primary winding, resulting in ignition problems such as misfiring.